In the present work,we have simulated the structure i-ZnO/n-CdS/p-CZTS/Mo based on copper-zinc-tin-sulphur(CZTS).CZTS has become a candidate material for new photovoltaic solar cell because of its excellent properties.We have used solar cell capacitance simulator one-dimensional(SCAPS-1D)to examine the impact of bandgap and thickness of CZTS on the performance of solar cells.It has been obtained the efficiency of 15.04% for the optimum thickness of 2,000 nm and the bandgap of 1.4 eV.For the best performance cell FF = 76.28%,Jsc = 23.51 mA/cm2,and Voc = 0.84 V.